Numerous medical operations require use of retractor devices that engage and manipulate body vessels in order to eliminate them as an obstruction or an interference during the operation. Movement of the body vessel or vessels away from the operation area is also intended to safeguard the vessel or vessels from unwanted contact or damage during the operation.
A particular medical procedure that requires body vessel retraction is an anterior spinal fusion procedure. This medical procedure is performed when intractable low back pain exists and non-operative treatments have proven to be unsatisfactory. The common cause for such intractable low back pain relates to a disc that is failing to function as a satisfactory shock absorber with resultant disc space collapse and with narrowing of the intervertebral space. The space that is available for exiting nerve roots also diminishes. Other causes for the intractable pain can relate to instability of the spine.
Anterior surgical procedures have significant advantage, in comparison with posterior procedures, in terms of time of recovery, morbidity of the operation and length of hospitalization. These attributes are realized because abdominal surgery for spine fusion tends to be a less invasive process than the posterior procedures due to decreased blood loss, decreased risk of infection and markedly less destructive approach to the spine. Anterior procedures also have the advantage of applying spinal fixation techniques which do not employ temporary internal splints, such as the case with posterior procedures which typically involve pedicle screws and rods. In the typical posterior spinal fusion, there is about a 30% chance that the posterior instrumentation will need to be removed within one year of implantation.
Patients undergoing the anterior spinal procedure can have the operation performed using a variety of different spinal fusion cages. These are devices placed within the disc space after thorough debridement of the area which allow for interbody fusion to take place using the patient's own bone packed into the fusion cage. The cage tends to distract the disc space to a point of original disk height thereby allowing increased space for neural exit from the spinal canal and restoration of the normal contour of the spine. In most instances, anterior cage fusions are confined to one or two level spine fusions, while procedures that involve arthrodesis or fusion of more levels require posterior segmental instrumentation, as well as an anterior fusion in order to increase the likelihood of fusion and increase the structural stability of the construct.
Selected patients with certain conditions have an option of a laparoscopic approach to the lumbar spine when their disease process is confined to the L5-S1 level of the spine. This procedure involves a general anesthetic for the patient and then placement of a laparoscopic portal beneath the umbilicus. The abdomen is then insufflated with carbon dioxide, thereby allowing an increase in the potential space available for the abdominal contents. The patient is then placed in the Trendelenburg position which allows the abdominal contents to fall towards the diaphragm and away from the lower portion of the spine where the operation is to take place. A laparoscope is then placed within the patient's abdominal cavity and exploration is carried out to make certain that there are no adhesions between an intestine and abdominal wall or between abdominal viscera and the L5-S1 area. Once clear visualization of the abdominal cavity has taken place, sites for additional portals in the lower quadrants of the abdomen are identified and it is through these portals that exposure of the L5-S1 interval is carried out. This involves tying off the median sacral blood vessels that tend to course directly over the L5-S1 interval. It also involves freeing up and mobilizing the iliac vessels as they traverse along the side of the L5-S1 disc. Once this process has been completed, it is then necessary to provide retraction of the great-in-size or diameter vessels so that they are out of the way of sharp reaming and disc preparation devices which are inserted through a separate portal above the pubis bone. These great vessels are typically 1 to 2 cm in size. The most serious and grave complications of anterior spinal fusions relate to injury to these great vessels. If the great vessels are injured during the course of the procedure, it necessitates emergency laparotomy or opening the abdomen in order to repair the vessels. There is potential for large volume blood loss and injury to the blood supply to the extremity and possible death of the patient. It is clear that great vessel retraction is mandatory in order to perform the procedure safely.
The currently available retractor for movement of the great vessels during an anterior spinal fusion procedure is identified as a laparoscopic peanut elevator. This device resembles a pencil with an eraser on the tip and it is the eraser tip that is used to help move the vessel away from the surgical area. This prior art device offers retraction only as wide as the device itself, which is typically 5 mm. This prior art retractor has certain drawbacks. It allows bulging of the great vessel around its edges and can allow vessel tissue to escape beneath it as well. Furthermore, such a prior art retractor may not allow for adequate visualization of the disc and the great vessels during performance of the medical procedure.
Because of these drawbacks associated with the currently utilized retractor, it would be advantageous to provide a retractor assembly that is sufficiently strong to eliminate unwanted bulging while making sure that the retractor assembly does not constitute a source of visual interference or obstruction.